1. Field of the Invention
The present invention relates to an automotive alternator mounted on a car, truck, or the like, and more particularly, to an automotive alternator including a brush unit with an improved discharge mechanism.
2. Description of the Related Art
A conventional automotive alternator generally includes: a slip ring provided on a rotation shaft of a rotor supported by a frame; a brush held in sliding contact with the slip ring; a brush holder for elastically pushing and holding the brush against the slip ring with a spring; and a substantially hollow cylindrical slip ring cover having an end attached to the frame to be coaxially spaced from the slip ring and surrounding substantially the entire periphery of the slip ring. Therefore, foreign matters such as water and oil are prevented from entering a slide portion between the slip ring and the brush. Further, in order to discharge water or the like having entered the slip ring cover, a discharge port is formed at a bottom in a gravitational direction of the slip ring cover (see, for example, Japanese Patent Application Laid-open Nos. 2002-359951 and 2006-6000).
In the above-mentioned conventional automotive alternator, the discharge port of the slip ring cover needs to be provided at the bottom. Therefore, parts having the same function as the brush units but having different positional relationships of the discharge port relative to the brush holder must be prepared so that the discharge port may be provided at the bottom when the brush holder is attached in different postures. This leads to a problem of increased number of models and parts.
In a case where the brush is pushed up when mounted in a vehicle, the structure of the brush unit disclosed in Japanese Patent Application Laid-open No. 2002-359951 cannot prevent the entry of foreign matters. Japanese Patent Application Laid-open No. 2006-6000 discloses a brush unit that prevents the entry of foreign matters for only the case where the brush is pushed up, but the structure does not support cases other than the case where the brush is pushed up.